The present invention relates to methods and apparatus for controlling medical hyperthermia or hypothermia treatments for humans and other animals, and more specifically for automatically controlling temperatures and rates of change of temperature in the subject of a perfusion hyperthermia or hypothermia treatment using a programmed computer system.
Fever is one mechanism by which a mammal fights disease. A number of pathogens, including some bacteria, some cancers, and some viruses, such as the HIV retrovirus and other enveloped viruses, seem to be adversely affected by heat. In addition, certain processes which normally fight disease, such as tumor necrosis factor A, seem to be stimulated with hyperthermia. Fever can be thought of as a natural-response hyperthermia treatment of a mammal to a pathogen or disease condition which may have a more adverse effect on the pathogen or diseased tissue than on the rest of the animal""s body, thus allowing the body to prevail against the disease condition.
In particular, artificially-induced whole-body hyperthermia, as opposed to, for instance, local application of heat to a tumor or extracorporeal hyperthermia treatments to blood, may be required to treat such diseases as HIV infection or a metastasized cancer where the pathogen is universally distributed in the experimental subject or clinical patient, since leaving any one part of the patient cooler (i.e., outside the boundary of the hyperthermia treatment) will provide a safe harbor for the pathogen, which will again spread into the rest of the body once the hyperthermia treatment ends.
Hippocrates first described hyperthermia treatments, around 480 BC, which used hot sand baths for patients with skin tumors. In 1927, a Nobel prize was awarded to a doctor, Warner Jauregg who used malaria-induced fever to treat syphilis. However, by the mid-1930s the medical community began to recognize the potential hazards of hyperthermic therapy, and a 1934 survey by the Council on Physical Therapy of the American Medical Association documented 29 deaths resulting from hyperthermia treatments. Among the adverse effects of hyperthermia are increases in cardiac output by as much as 200% of normal, increases in oxygen consumption, changes in serum enzymes, drops in phosphate, calcium, and magnesium levels, heart, liver and brain damage and failure, disseminated intravasular coagulation, hemolysis of red blood cells, spinal-cord necrosis, fluid loss from diuresis and perspiration, electrolyte shifts, and bleeding problems associated with systemic heparinization.
Hyperthermia has been induced using hot baths, bacterial inoculation, hot wax, hot air systems, heated water blankets, etc.
Hyperthermia has been combined with radiation and/or chemotherapy to achieve synergistic results against cancers (i.e., when heat is combined with those other therapies, destruction of neoplastic tissues occurs at smaller dosages of radiation or chemotherapy agents).
One shortcoming of prior-art systems and methods has been the lack of tight, fast, and automatic control over, and lack of visual feedback with respect to, the exact temperature achieved in particular parts of the body of the patient, the average temperatures of the body core or various body parts, the rates of temperature change, and temperature gradients between various body parts. In addition, known prior-art perfusion hyperthermia systems have not automated system checklists, patient-monitoring systems, alarms, treatment-procedure recording, nor the monitor indications and controls provided to the medical professionals who administer the hyperthermia treatment.
What is needed, and what the present invention provides, is a system and method that automatically monitors and controls a perfusion hyperthermia treatment using a system including one or more programmed computers, and mechanical and sensor subsystems. The system includes a fluid path between a patient and an external fluid-treatment subsystem, wherein control of the external fluid-treatment subsystem includes feedback from sensors coupled to the patient. The resulting integrated system provides an automated monitoring and control of the patient, the external fluid-treatment subsystem, and the treatment. In one embodiment, the fluid passing between the patient and the external fluid-treatment subsystem is blood.
In one embodiment, an apparatus and method are provided for using a computerized system for a perfusion hyper/hypothermia treatment of a patient which obtains a body fluid having a particular temperature. A plurality of temperature signals representative of temperatures at each of a plurality of patient locations on or within the patient are coupled to the computer system. Measured temperatures are compared to a set of stored parameters in the computer system to generate a comparison value which controls a change in the temperature of the body fluid which is made by the extracorporeal fluid-treatment system. The body fluid is then perfused into the patient to either warm, cool, or maintain the current temperature of the patient. In one such embodiment, the body fluid is blood withdrawn from the patient. In another such embodiment, the body fluid is saline.
In one embodiment, the supply voltage to the plurality of thermistors is provided by a circuit which provides a very short pulse, one at a time and sequentially to each thermistor, in order to reduce heating of the thermistors and to reduce the electrical hazards, and via a multiplexor, couples the analog response signal to an A/D convertor.
In one embodiment, the mass of water in the water circuit is minimized in order to improve the response time of the temperature control feedback mechanism.
In one embodiment, the volume of blood in the blood circuit is minimized in order to reduce the amount of blood outside the patient and to improve the response time of the temperature control feedback mechanism.
In one embodiment, a rate of change of temperature is measured and controlled according to a stored parameter in the computer system.
In a further embodiment, checklist input is elicited and received from a user, and used to control operation of the computer system.
In another further embodiment, correct operation of the computer system is repeatedly verified with a self-test program.
In another further embodiment, correct coupling of the computer system to external components is repeatedly verified with a self-test program.
One embodiment also provides a visualization of the monitored functions.
One embodiment also provides a recording over time of one or more of a set of measured parameters.
One embodiment provides for an integrated disposable body-fluid subsystem which mates with a reusable system interface.